Stents are commonly used for the treatment of body passages afflicted with hard irregular, masses, such as stones and stone fragments. Stones and stone fragments frequently develop within the urinary tract, including the kidneys, ureters, bladder, and the urethra, and can also develop in the other specific body passages, such as the biliary, salivary, and vascular passages. Conventional stents, such as the stent described in U.S. Pat. No. 5,129,910, for treatment of such masses comprise an elongate, flexible tubular body and generally include a central lumen extending the length of the body. Typically, the stent is provided with a series of spaced-apart barriers in the form of a ridge disposed along a portion of the stent body for urging the masses out of the body.
During treatment, the stent is inserted into the afflicted body passage and provides for passage of fluid through the lumen. The stones and stone fragments are urged out of the body passages either through the lumen or along the exterior surface of the stent. At the conclusion of the treatment, the stent is removed from the body passage.
Problems have developed with use of such stents due to the tendency of the stents to fracture within the body passage. Crystal encrustation of the stent during implantation results in a loss of elasticity leading to an increased likelihood of fracturing. Stent fracturing can occur during the treatment process or as the stent is removed from the body passage and is more likely during treatments requiring long term implantation of the stent. Fracturing can cause fragmenting of the stent into multiple pieces within the body passage and can result in stent fragments becoming lodged in the body passage. Removal of the stent fragments can be problematic, often requiring additional medical procedures and even surgery.
As such, there is a need for a stent for maintaining the patency of body passages that includes a reinforcing element for inhibiting the fracturing of the stent and aiding in removal of the stent.
Other problems are known with conventional stents. Specifically, reflux, particularly during treatment of the urinary tract, often occurs with such stents, resulting in the passage of fluid within the lumen of stent in a direction opposite the intended direction. During treatment of the urinary tract, the stent is inserted into the ureter between the kidney and the bladder and provides for fluid (urine) passage from the kidney to the bladder through the lumen of the stent. As bladder pressure increases, urine reflux occurs and urine begins to pass through the stent from the bladder back into the ureter, and potentially to the kidney.
As such, there is a need for a stent for maintaining the patency of a body passage that decreases reflux through the stent lumen.
It is an object of the invention to provide a reinforced stent for maintaining the patency of body passages that is less likely to fracture during treatment of the body passage.
It is another object of the invention to provide a stent for maintaining the patency of a body passage that decreases reflux through the stent.
It is a further object of the present invention to provide a stent that is inexpensive to manufacture and easy to use.